Hi there,
Bolivians are notoriously difficult to sex, hence I suspect the lack of replies. Unfortunately traits like finnage and colouration are not that reliable for determining which sex you have.
I have seen the comments / rumours that the best way to sex Bolivians is > the 1 laying the eggs is the female and if you end up with fry then you have a pair
On saying that, as you suggest in pic 2, if the ovipositor is fully extended and remains flat, then it is likely to be a female (the male ovipositor should come to a point).
Andrew